Ensure assert_valid_syn_id() is always called with correct thread id

[heplesser]

Automated thread analysis revealed a data race because ModelManager::get_connection_model() calls assert_valid_syn_id() without thread argument

nest-simulator/nestkernel/model_manager.h

Line 303 in d5aa3fe

assert_valid_syn_id( syn_id );

thus using the default thread number 0. This can lead to data races during parallel construction of new models during CopyModel. This PR removes the default value for the thread so avoid data races.

[otcathatsya]

Looks good; would it be an option to set the current thread id as the parameter default? From what I can see the method is only used inside connection and model manager who always call it with the same parameterization.

[heplesser]

Looks good; would it be an option to set the current thread id as the parameter default? From what I can see the method is only used inside connection and model manager who always call it with the same parameterization.

The parameter default must be a constant, so we can't make the current thread the default.

[otcathatsya]

Looks good; would it be an option to set the current thread id as the parameter default? From what I can see the method is only used inside connection and model manager who always call it with the same parameterization.

The parameter default must be a constant, so we can't make the current thread the default.

My bad; could do an overload to produce the same behaviour?

[suku248]

Looks good, thanks @heplesser